1. Field of the Invention
This invention relates to a molded plastic mounting part formed as a base for function parts on a metal supporting plate, which mounting part, in order to be mounted on this plate, has a bridge element traversing a hole in the metal supporting plate, and retaining elements which bear against both plate surfaces of the metal supporting plate.
2. Description of Related Art
Mounting parts molded onto metal supporting plates are known, for example, from "Feinwerktechnik und Me.beta.technik", Volume 87, No. 6, September 1979, pp. 253 to 259. The technique of manufacturing such mounting parts in combination with metal supporting plates is known by the name of outsert-molding technique. The mounting parts molded onto the metal supporting plate are intended for a variety of purposes, such as retaining, supporting or guiding the function parts. The function parts can be, for example, bearings, gear wheels, sliders, levers or spindles. The molded-on mounting parts and the supporting plate are always joined in that plastic retaining elements overlap edge portions of holes in the plates at the upper side and the underside of the plate and in that the plastic retaining elements are interconnected by a plastic bridge element traversing the hole. The plastic bridge element can be solid but it can also be internally hollow, taking the form of a sleeve.
Moreover, it is known that the cooling process, which begins after the plastic has been molded on, is accompanied by shrinkage of the plastic. This shrinkage takes place in all directions, i.e. in the longitudinal direction of the bridge element and in a direction perpendicular thereto. The shrinkage in the longitudinal direction of the bridge element results in a tighter fit of the retaining elements on the plate surfaces. The shrinkage in a direction transverse to the longitudinal direction results in an undesirable clearance between the wall of the hole in the metal mounting plate and the outer wall of the bridge element traversing the hole. As a result of this clearance, the accurate fit of a mounting part with respect to the hole is no longer exactly predetermined. The axis of the mounting part and the axis of the hole no longer coincide in a reliable manner and may become displaced with respect to one another.